As a load detection device, for example, one described in JP 2012-32312A (Reference 1) is known from the past. The load detection device includes a load sensor and a control device (ECU) connected to the load sensor so as to perform bidirectional communication. Then, the load sensor includes a load detection element outputting a load detection signal corresponding to a load to be applied to a seat body and a first controller (controller) which acquires load information based on the load detection signal. The first controller is configured to acquire failure information together based on magnitude relation between the load detection signal and a threshold signal corresponding to a threshold for detecting a failure. This is because there is a high possibility that a phenomenon (failure) requiring repair such as vehicle collision occurs, for example, when the load detection signal is excessive.
On the other hand, the control device includes a second controller (CPU) receiving load information and failure information from the load sensor. The second controller determines presence of an occupant, that is, whether the seat is vacant or occupied based on the load information. The second controller also drives an indicator to make notification to promote, for example, repair based on failure information.
Incidentally, in Reference 1, the second controller just receives failure information depending on the first controller and performs necessary processing in accordance with the failure information. This is because a communication period of the second controller which receives load information and so on is set to be significantly longer than an arithmetic period of the first controller which acquires load information and it is difficult to shorten the communication period of the second controller so as to obtain failure information by itself.
On the other hand, the first controller acquires failure information only based on the magnitude relation between the load detection signal and the threshold signal, therefore, the reliability thereof is naturally limited. Accordingly, for example, there is a possibility that the notification to promote repair is made by the second controller uselessly, though the repair is not necessary.